Subtotal villous atrophy in the proximal jejunum was observed in six patients affected by juvenile diabetes. Introduction of gluten free diet invariably led to clinical improvement, in the four patients in whom also rebiopsy was performed the jejunal mucosa exhibited improvement. In all cases gluten sensitive enteropathy was diagnosed after the onset of diabetes. Marked stunting in growth, strikingly labile carbohydrate tolerance, pronounced proneness to hypoglycaemia or development of Mauriac's syndrome were the symptoms pointing to coeliac disease. Protracted diarrhoea was seen only in two patients, pronounced deceleration in weight development occurred in none of the six children. In four patients out of six the presence of both HLA B8 and DR3 antigens was demonstrated, in a fifth patient only DR3 was present; this suggests a common genetic background of the simultaneous occurrence of the two disorders. Untreated coeliac disease aggravates preexisting diabetes. The importance of early recognition of latent coeliac disease is stressed.